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Re: 8bit Apples - Apple I, II, /// and the 16 bit GS [Re: AJR] #117549 07/13/20 09:32 PM
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Golden Child Online Content
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Hi AJR,

I've been reading the upd7810 datasheet and yes, you're right, the NMI shouldn't get stopped by the iff (interrupt enable flip flop).

I did come across this while trying to understand the interrupt flags:

It looks like the INTOV flag is kept in the IRR but it gets set in the ITF.

Code
grep INTOV src/devices/cpu/upd7810/ -r
src/devices/cpu/upd7810/upd7810_opcodes.cpp:	if (IRR & INTOV)
src/devices/cpu/upd7810/upd7810_opcodes.cpp:	IRR &= ~INTOV;
src/devices/cpu/upd7810/upd7810_opcodes.cpp:	if (0 == (IRR & INTOV))
src/devices/cpu/upd7810/upd7810_opcodes.cpp:	IRR &= ~INTOV;
src/devices/cpu/upd7810/upd7810.h:		INTOV   = 0x1000,
src/devices/cpu/upd7810/upd7810.cpp:					ITF |= INTOV;   /* set overflow flag if counter wrapped */

Re: 8bit Apples - Apple I, II, /// and the 16 bit GS [Re: rfka01] #117618 08/02/20 10:40 PM
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R. Belmont Online Content
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We now have Apple IIe RGB card support, which adds a handful of interesting video enhancements that had surprising amounts of software support. See more here: https://rbelmont.mameworld.info/?p=1389

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